The present invention generally relates to a system for safely storing hydrogen gas so that the hydrogen gas can be charged into the system, safely stored, and discharged from the system upon demand. More particularly, the present invention relates to storage cells which can be contiguously assembled to produce a hydrogen storage system.
Hydrogen gas, H.sub.2, is a well known substance which has many advantageous characteristics. One such advantageous characteristic is that hydrogen gas can be utilized as a combustible fuel which is clean, efficient and produces no harmful product of combustion. Hydrogen gas when utilized as a combustible fuel yields water, H.sub.2 O, as a product of the combustion reaction.
However, an extreme disadvantage to the use of hydrogen as a combustible fuel relates to the extreme volatility inherent with hydrogen gas. Hydrogen is relatively stable at ordinary temperatures, but is extremely flammable in the presence of oxygen and reacts spontaneously when activated by a flame or electric spark, or in the presence of a suitable catalyst. The combustible reaction of hydrogen and oxygen to produce water is exothermic and will explode violently when the proper ratios of hydrogen and oxygen are ignited.
The inherent dangers in utilizing hydrogen as a fuel source has prevented hydrogen from becoming widely accepted as a commercially viable alternative to fossile fuels, such as, oil, natural gas or the like. Thus, it has been impractical to use hydrogen gas as an alternative fuel source since it would be extremely dangerous to store the hydrogen gas prior to beneficially using it as a fuel.
It has been proposed to contact hydrogen gas with a hydridable material such that the hydrogen gas is stored in the form of a hydride. This form of storage renders the hydrogen gas relatively inert thereby increasing the confidence and safety in using hydrogen as a fuel source. A typical storage system utilizing the hydride storage of hydrogen gas is disclosed in U.K. Pat. No. 2,015,142, the disclosure of which is incorporated herein by reference. Typical conventional storage systems provide a plurality of container-like storage cells with each cell utilizing a hydrogen gas permeable membrane. The hydridable material is stored within each of the individual storage cells such that the hydrogen gas introduced into the complete system permeates through the membrane and is stored in the form of a hydride therein.
A problem which has been associated with conventional hydrogen permeable membranes utilized in the individual storage cells is the possibility that the hydridable material will block the free permeation of hydrogen gas causing a sudden high pressure build up with the possibility of rupturing the storage system. The hydridable material conventionally used in such storage systems is Lanthanum Nickelide, LaNi.sub.5, a Fe/Ti alloy or like material. The hydridable material, such as, for example, Lanthanum Nickelide is placed in the individual conventional storage cells and hydrogen gas is allowed to permeate into the crushed or powdered material.
The hydrogen gas when contacted with the Lanthanum Nickelide hydridable material forms a hydride. Hydridable materials, such as, for example, Lanthanum Nickelide and Titanium Iron, readily absorb hydrogen gas at room temperature after first being activated by an elevation of temperature. Once the hydrogen gas is charged in the system in the form of a hydride, it may be liberated or discharged by the addition of heat to the hydridable material. After a number of charge/discharge cycles, the Lanthanum Nickelide or similar hydridable material experiences an automatic comminution to submicron powders. It is the submicron powders of the hydridable material which, in some cases, can cause blockage of the permeable membrane associated with conventional hydrogen storage cells.
Therefore, according to the present invention, there is provided storage cells and systems utilizing a plurality of such storage cells whereby the hydrogen gas is allowed to permeate through the membrane associated with the storage cell while the submicron powders of a hydridable material are impermeable therethrough. This is accomplished according to the method and apparatus of the present invention basically by coating a screen, which may have a variety of forms, with a ceramic material which will allow the passage of hydrogen, but not the passage of submicron particles of the hydridable material such as LaNI.sub.5. The ceramic material may comprise a fired aqueous binder solution which includes aluminum phosphate, a soluable chromium compound, and an organic amine compound, such as the commercially available "ALSEAL 502".
Thus, according to the present invention, a safe system of storing hydrogen gas is provided such that the possibility of cell rupture due to high pressure build-up is avoided. By utilizing a storage system according to the present invention, hydrogen gas can be confidently and safely relied upon on a commercially large scale basis as a reasonable alternative to fossile fuels. Thus, it is entirely conceivable that machinery or automobiles utilizing an internal combustion engine and equipped with a storage system according to the present invention will be able to use hydrogen gas as a safe, efficient, and clean fuel for power.